1. Field of the Invention
This invention relates to a high resolution digital suspension position sensor for an automotive vehicle.
2. Disclosure Information
Automotive suspensions employing adjustable suspension units typically utilize one or more sensors for detecting the position of one or more portions of the suspension with respect to either another part of the suspension itself or another part of the chassis of the vehicle. In the case of vehicles using load leveling or air or hydropneumatic suspension systems, it is necessary to know the ride height of the vehicle in order to determine whether correction of the ride height is required. In the event, for example, that the ride height is lower than a prescribed "trim" limit, as determined by the height sensor, an adjustable suspension unit may be given a command to increase ride height. Conversely, in the event that the ride height exceeds the prescribed "trim" limit, the adjustable suspension unit may be given a command to lower, or decrease, the ride height.
Vehicular height sensors are useful not only with ride height adjusting systems but also as transducers for use with adjustable suspension dampers. A sensor according to the present invention is useful for providing not only suspension position information but also ride height information for use with a vehicle leveling system or an air or hydropneumatic adjustable suspension or other type of adjustable suspension system.
U.S. Pat. No. 4,105,216 discloses a motor vehicle level control circuit in which a pair of optical detectors interacts with a rotary shutter device to produce a first logic signal pair when the vehicle's ride height is in a trim region, and second and third logic signal pairs when the vehicle's ride height is either high or low and out of the trim region. The system of the '216 patent has the capability of producing only three logic signal pairs with two detector devices. A sensor according to the present invention, however, will easily have the capability to produce, with only three detector devices, a digital output defining thirty-two or more ride height states. For this reason, the present sensor is deemed to be a "high resolution sensor".
U.S. Pat. No. 4,453,725 discloses a rotary height sensor using a bifurcated shutter and three optical devices in order to produce a sensor which resolves vehicle ride height into five possible levels.
U.S. Pat. No. 4,433,849 discloses a vehicle leveling system having two reference vehicle height positions requiring separate detectors for each reference vehicle ride height position.
U.S. patent application No. 126,082, entitled "Automotive Suspension Control System Including Suspension Position Sensor", which was filed on Nov. 27, 1987, and which is assigned to the assignee of the present invention, discloses a vehicle height sensor in which two detector devices are used to produce a digital output having four discrete states.
A variety of sensing techniques have been employed with vehicular height sensors. These include, without limitation, electro-optical devices, linear variable differential transformers, and Hall Effect devices. Examples of the latter are disclosed in U.S. Pat. Nos. 3,473,109; 4,107,604; 4,204,158; and 4,555,120, which are hereby incorporated by reference. U.S. Pat. 4,310,172 discloses an adjustable suspension unit having an internal Hall Effect ride height sensor of conventional design. A sensor according to the present invention may utilize Hall Effect detectors or electromagnetic reed switches, or optical devices, or yet other types of known detecting devices.
It is an object of the present invention to provide a digital output height sensor capable of accommodating a plurality of reference vehicle ride height positions with a single height sensor containing only three detectors.
It is an advantage of the present invention that a suspension position sensor according to this invention will furnish much more information than prior art sensors having a like number of detector devices.
Other objects, features and advantages of the present invention will become apparent those skilled in the art to which this invention pertains.